Renderer: Add initTexture().

[Mugen87]

Related issue: #29898 (comment)

Description

The PR adds initTexture() in a snyc and async version so it is possible to avoid the texture decode overhead when textures are used in the first frame.

I've verified the implementation with the WebGPU and WebGL backend by making sure the below texture decode metric does not appear in Chrome's performance analysis tool when rendering the first frame:

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	339.13 79	339.13 79	+0 B +0 B
WebGPU	482.5 133.72	482.81 133.76	+311 B +36 B
WebGPU Nodes	481.96 133.62	482.27 133.66	+311 B +37 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	464.59 111.96	464.59 111.96	+0 B +0 B
WebGPU	550.56 149.19	550.87 149.23	+311 B +36 B
WebGPU Nodes	506.44 138.91	506.75 138.95	+311 B +36 B